<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        div{
            width: 200px;
            height: 200px;
            background-color: skyblue;
            border-top:4px solid red;   
            /* 上边框线属性 */
            border-left:2px solid black; 
            /* 左边框 */
            border-right:2px solid black;
            /* 右边框 */
            border-bottom:4px solid red;
            /* 底部边框 */
        }
    </style>
</head>
<body>
    <div>testtest</div>
</body>
</html>